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This blog is about speculative biology. Recurrent themes are biomechanics, the works of other world builders, and, of course, the planet Furaha.

Thursday, 27 May 2010

"Into the universe" and right off a cliff

In my last post I promised to report back on any interesting alien animals in the recent Discovery Channel series 'Into the Universe with Stephen Hawking'. Well, the Discovery Channel has the relevant footage on its site, right here. Some of the images of the program on aliens are rather nice, particularly where the computer generated imagery concerns space hardware. The underwater creatures and the ballonts weren't bad either. One life form really caught my attention however, but I cannot say I am positively impressed. Have a look at the following video.

I was interested right up to the point where camera rotates to reveal that the animal is in fact clinging to a vertical rock surface. Until then I thought that the mouth design was kind of interesting, scraping algae or their equivalents off a flat surface. You could debate on how well it would work, and that would be fun. But the rather large problem is how the animal manages to cling to a vertical rock surface.

It pays to think about the forces needed to keep an object fixed to a vertical surface. The centre of gravity of the object will be some distance away from the wall, producing a lever effect on the contact area. Think of a painting hanging from a nail: the top pulls away from the wall while the bottom presses against it. If you had to fix a heavy object to a wall with only one screw, you would put it in where you have to counteract a pulling force: at the top. The bottom of the contact area will stay against the wall anyway. In short, the top end of the contact area pulls away from the surface and the bottom end presses against it.

This also holds for rock-climbing humans. Feet press against the wall, but fingers pull on it. This is much easier if there are gaps the fingers can be hooked into, as otherwise friction is the only force to stop the body tumbling down. Keeping the body close to the rock minimises how hard the fingers have to pull, so the less secure the grip is, the closer you will want to stay near the surface. The same principles are at work on a woodpecker on a tree trunk: woodpeckers rest their stiff tails against the the bottom contact point, and their claws, the top contact area, dig into the bark and pull on it.

Click to enlarge; copyright Discovery channel

Back to Discovery's 'rocksucking cliffhanger' (as it appears to be nameless I made that name up). The image above was taken from the video, but was rotated to show the animal in its vertical position. It has two legs at the bottom, and at the top the mouth is the obvious device to pull on the rock surface. I must say that this is in itself a rather nice idea. You may argue that such a large mouth would need improbably large flat areas, or that dust, snow or rain water could really make life difficult, but such matters might be worked out.

Click to enlarge; copyright Gert van Dijk

In the sketch above you see my take on the situation (marked A). The body is held fairly far away from the cliff wall, meaning that there are serious lever effects. A line connects the centre of gravity with the lowest point of contact, where rotating forces will push the feet against the rock. The mouth has to suck rather hard to prevent a fall (blue arrow). But what happens if the animal lets go with its mouth, as in sketch B? Ah, right... No cliffhanger here: it will fall, and I can think of only two ways to stop it doing so. The first is that the new top contact area, the toes, must exert an unbelievably strong sucking ability; that possibility is shown here, but I see no evidence of that, and it is very impractical. The other way would be for the cliffhanger to shift its mouth to a new position extremely quickly, before the body has moved downwards so far that there is no stopping it anymore. The video shows that repositioning the mouth takes about one second. On earth an object will in principle fall 4.9 meters in the first second of a fall! This distance would be less on a low-gravity world, and I do not know how many body-lengths that is, as there is no size indication. Still, it sounds as if the fall would then be unstoppable. You would want the loss of sucking power to last as short as possible: it it would only last for 0.1 second, the animal's centre of gravity would only move downwards by 4.9 cm. The process had better be failsafe though; no second chances here. A much better solution would be to having two or more sucking devices, as their use could then be alternated.

As shown, I do not see the animal working as designed. It's a pity, really. As with Avatar, it would not have been that difficult to get someone to have a critical look and iron out the problems. It's not rocket science, after all. Why do companies as big as Discovery let such matters slip? The only answers seem to be that they take science a lot less seriously than they pretend to do, or that they do not take their audience seriously. I am very much in favour of science popularisation, but fumbling it gives the wrong idea.

9 comments:

I think that's the most obviously flawed design of any purportedly serious attempt at alien life that i've ever seen. You don't even have to know anything about biology to see that it wouldn't work.

Of course the biology is dubious too. Climbing vertical cliffs largely by suction has to be a high calorie life-style. Yet we have huge herds of apparently very large animals subsisting on some algae/lichen analog that is so sparse it doesn't even visibly discolor the rock face.

I noticed this problem too when I watched the show and my first thought was that the cliffgrazer (that's what I'm calling it) must have a REALLY light body structure, with hidrogen bladders inside and everything...

Your arguments run similar to mine: if this animal is to be believable, then it has to be extremely light, either because it lives on a low-gravity world, or because its mass is tiny. Both cases ought to result in a similar build. I am preparing one or two posts on how limb thickness scales in relation to body mass and gravity.

The problem is that right now the cliffhanger/grazer's limbs look like they are built to move a fairly large mass around. They do not look like an insect's limbs at all, which is why I opted for the unpleasant explanation that someone did not put enough thought into these creatures. I doubt that Hawking himself is to blame. Commercial television is the more likely culprit: beyond a certain superficial effort there is no -material- gain in getting things right.

With it's tiny (relative to body size) lensed eyes, and rapid rate of falling when the yellow, gliding predators attacked it gives every evidence of being a large, heavy creature on a world with gravity similar to ours.

Eyes are a good way to judge scale, since they don't need to scale with the creature like limbs and bones.

If gravity were low, and or it had gas bladders to make it significantly less heavy, it should have fallen more slowly.

Who knows, I would have guessed that the cliff-climbing was an afterthought, added in at the last minute to make the stolid herbivore more interesting, but the yellow glider seems to have been designed with cliff-climbing prey in mind.

Even if they had just made it climb head down it would have made a lot more sense.

Re: Orb maps:Thanks, Sigmund.

My 3D skills are limited, but all i need right now is a way to see the Orb as a round globe so i can avoid polar distortions. This method: http://tinyurl.com/25ccypv works for that, but i may call on you at a later stage in production.

Ever since the "second brain" fiasco regarding the Discovery program "Clash of the Dinosaurs", Discovery Channel's been notorious for twisting the facts around to make more interesting television, as well as showing they have a very low opinion of their audience.

In the aforementioned case with Clash of the Dinosaurs, the Discovery Channel had tried to nix the true identity of the glycogen body by claiming it was "too complicated" for viewers, even when the interviewed scientist basically summed the concept up as "The most likely object in the cavity of the hips of large dinosaurs is a glycogen body, which birds have today. However, we don't know what it does."

In addition, they had been pushing the scientist to try and advocate the inaccurate claim that sauropods and stegosaurs had a second brain, and when that failed they resorted to good old manipulation of the film to get what they wanted. It seems likely that the reason for the choice of these creatures habitat is about the same as that of the glycogen body, the execs thought it would make better television. This is truly a sad case of misrepresentation of science.

Why not simply put more suckers on the rocksucking cliffhanger? I mean, most animals in the world today have more than two limbs, and it would make sense for the cliffhanger to devote more than just its mouth to retaining its suction on the wall, especially given its height. The cliffhangers in the clip do have arms, but these seem vestigial.

What is interesting is the idea of a habitat dominated by sloping grounds or nearly sheer cliff-like surfaces. How would this kind of habitat evolve? Would it arise in a manner similar to the strange rock formations of Madagascar or the canyons of the Colorado Plateau, but on a large scale? And what kind of creatures would inhabit them? My guess would be that many of the species might be flying organisms, with a hummingbird-like wing to help them hover in place to help scrape lichen off walls, or else cling to the wall with claws while they are grazing.